如何判断是否不是数字或字母

import re

def is_not_alnum(char):
    return not re.match(r'^[a-zA-Z0-9]$', char)

# 示例
print(is_not_alnum('a'))  # False
print(is_not_alnum('1'))  # False
print(is_not_alnum('@'))  # True

def is_not_alnum(char):
    return not ('a' <= char <= 'z' or 'A' <= char <= 'Z' or '0' <= char <= '9')

# 示例
print(is_not_alnum('a'))  # False
print(is_not_alnum('1'))  # False
print(is_not_alnum('@'))  # True

def is_not_alnum(char):
    return not char.isalnum()

# 示例
print(is_not_alnum('a'))  # False
print(is_not_alnum('1'))  # False
print(is_not_alnum('@'))  # True